Testing system for nontyping selectors



rolas W52?. D. ELFOLEY ET AL TESTING SYSTEM FOR NON-TYPING SELEC Filed March l, 1945 W j@ im 5 n MW WN T J m w m n if n@ ,LM

IN VE N TORS 12m/Lid EZm'o/fe FUI@ ha@ lelf ame gjhl on ATTORNEY Patented Apr. l, 1947 rrits'rINo SYSTEM `Foa NoN'rYPING sELEo'roRs Daniel Elmore Foley,

Daniel Johnson,

Evanston, Chicago,

and Walter Ill., ass'gnors to American relephone and Telegraph Company, acorporation of NewYork Application March 1, 1945, Serial No. 580,394

systems. More particularly, this invention relates to'teletypewriter systems and apparatus and, still more particularly, to non-typing selector apparatus. The invention provides apparatus for testing non-typing selectors` and other teletypewriter apparatus.

In teletypewriter systems a modied form of teletypewriter, known as a non-typing selector, `is often used for switching or control purposes. Such a non-typing selector may be ateletypewriter, the typing mechanism of which has been removed or strapped so as to be inoperative. `The non-typing selector includes, amorg other things, an operating magnet and. its associated selective elements, together with a universal contact assembly and a plurality ci pull-baricorltact assemblies. The universal contact assembly may be selected by the magnet in response to the pulses corresponding to teletypewriter character Letters and then released shortly thereafter. When a character such as X is received by the non-typing selector to select the corresponding pull-bar assembly, the latter pull-bar assembly will normally be selected and the selection will be followed by the selection of the universal contact assembly. Not only are the pull-bar assembly corresponding to the character Xand the universal contact assemb'y closed in the order named `when the appropriate `assembly and the universal Contact assembly will beselected and operated in the order named and released shortly thereafter in the reverse order.

One of the requirements of the non-typing se# lector to insure its proper operation is vto have the closure time of `any of the pull-bar contacts exceed and fully overlap the closure time of the universal contact. It is important that each selected pull-barcontact should operate before the universal contact and thatit should release after the universal contact has released. `l-leretofore this Yrequirement was, seemingly satis'ledby making mechanical adjustments of the` various contacts. The mechanical adjustments, however, were sometimes found to beinsuicient to assure that the non-typing selector operated `properly. One of the objects o-fthis invention is, thereforethe provision of an electrical testing circuit to observe whether each ofthe various pull-bar contacts and the universal contact are ,operated and released 11.1; therme@ Sequence. ,The electa,- is

4 Claims.' (01; 17a-69) caltesting circuit of this invention includestan instrument, such as a telephone receiven, `for ina dicating by the presence or absence of `an audible signal that these contacts have operated in the proper sequence.

Another of the requirements of the non-typing selector to insure its proper operation is to have each of its `various pull-bar contacts or the uniersal contact remain closed for a specified or predetermined interval of time during each op eration of the pull-bar contacter the universal contact. This operating time interval can also be measured with the electrical testing circuit` of this invention by converting the measured current flow through the contact as it is repeatedly operated into appropriate units of time.

These-and other objects and features of this invention will be better understood from the more detailed description hereinafter following when read in connection with the accompanying draw.. ing illustrating one embodiment of the invention given merely for 'illustrative purposes.

In the drawing the non-typing `selector is designated NTS and a teletypewriter transmitterdistributor is designated TTY.. The transmitterdistributor TTY is of we1l-known type and produces aV group of pulses in accordance with each teletypewriter character to be transmittedto the non-typing selector NTS. The` transmitter-distributor is shown connected to the operating magnet MG of the nonft'yping selector. The no-ntyping selector NTSr `is also or' well known type. Apparatus suitable as a non-typing selector such as NTSis described in thel application Serial No. 383,490, filed March 15, 1941, by VV..1M. Bacon et al., now Patent No. 2,381,871, granted August 14, 1945. The disclosure of the Bacon et al. application may be considered as part of the present application. Y

The magnet MG of the NTS controls through appropriate selector mechanism A(not shown) a pluralityof pull-'bar contact assemblies, only three, of rwhichare shown and are designated X1, Y1 and Z1, and it also controls a universal contact assembly UV. Each pullfbar contact assembly as well as thefuniversal contact .assembly` include a swinger and two contacts on opposite sides of. the swingenas shown. I, The lowercontactof each of these assemblesiistnor'-, mallyelosed bythe swinger,` while 'the upnerconf. tact of the swinger is closed only uponthe'proper operation of thermagnetMG in responseto'a'n appropriate teletypewriter signal for.. character reeirvedi imm ,theatransmitter-distributor. T??- non-typing selector X1, Y1 and Z1 are strapped together and grounded and the ground is connected to the upper contact of the swinger of the universal contact assembly UV. The swinger of the universal contact assembly UV is connected to the lower terminal of resistor R2. The upper contacts of the pullbar contact assemblies are also strapped together and are connected to the terminal common to resistors R1 and R2. The resistor R1, the meter A and the battery B are connected in series with each other and to ground, as shown. The receiver TR is bridged across resistor R2 so that it may respond to any changes in voltage across resistor R2. The receiver TR may be replaced by any well known form of detector.

`To determine whether the closure time of a swinger of one of the pull-bar contact assemblies, such as X1, overlaps that of the universal contact assembly UV, the teletypewriter transmitterdistributor TTY is rst caused to send a Letters signal to the non-typing selector NTS. This will cause the swingerrof the universal contact assembly UV to close its upper contact and thereafter return to its lower contact. Upon the closure of the upper contact of the universal assembly UV, current will ow over a circuit eX- tending from battery B, through meter A, through resistors R1 and R2, through the swinger and upper contact of the universal assembly UV to ground. As the receiver TR is bridged across resistor R2, a click will be heard in the receiver. Thus, a click will be heard in the receiver TR for each operation of the non-typing selector NTS in response to the Letters signal. Now the teletypewriter transmitter-distributor TTY is caused to send the teletypewriter character X repeatedly to the non-'typing selector NTS. IIf the non-typing selector is operating properly, the swinger of the pull-bar contact assembly X, lirst will be moved to its upper contact. Current will .then flow over a circuit which includes battery B, meter A, resistor R1, the upper contact and swinger of assembly X1, and ground. VAt this moment no current will traverse resistor R2. Then the swinger of the universal assembly UV will close its upper contact. This Will complete the circuit previously describedthrough the swinger of the universal assembly UV. Therefore two circuits will be simultaneously established, one through the swinger of the pull-bar assembly X1 and the other through the swinger of the universal assembly UV. However, because of the greater resistance in the latter circuit dueto the inclusion of resistor R2 and receiver TR in parallel therein, all ofthe currentwill be'drained through the circuit of the swinger of the pull-bar assembly X1 and there will be no click in the receiver TR. Then the swinger Vof the universal assembly UV' will return to its lower contact without producing any current flow through the receiver TR. Finally, the swinger of the pull-bar assembly X1 will return to its lower contact, whereupon the flow of current from battery- B Will cease. This same 4cycle will be repeated again and againwith the next teletypewriter characters X received by i writer transmitter-distributor TTY. Thus, no clicks will be heard in receiver TR when the character X is received, provided the contact closure time of the pull-bar assembly X1 fully overlaps or masks the contact closure time of the universal assembly UV. Y

If the teletypewriter character Y is successively received by the non-typing selector NTS, a similar cycle will be repeated. The swinger of the pull-bar assembly Y1 will closeits upper contact, then the swinger of the universal assembly UV will close its upper contact, then the swinger of the universal assembly UV will return to its lower contact, and finally the swinger of the pull-bar assembly Y1 will beturn to its lower contact. However, there will be be no clicks in receiver TR if the upper contact of the pull-bar is clean and its closure time fully overlaps the closure time of the universal contact assembly U Suppose that the upper contact of the pull-bar assembly X1 is dirty when the characters X are received from the teletypewriter transmitterdistributor TTY. Then the closure of the upper contact of the pull-bar assembly X1 will complete a circuit therethrough of considerable re sistance. The parallel circuit subsequently completed through the swinger and upper contact of the universal assembly UV will carry an appreciable amount of current, the magnitude of the latter current depending on the contact resistance of the pull-bar assemblyY X1. If the contact resistance of the pull-bar assembly X1 is very large, then practically all of the current will be drained through the swinger of the universal assembly UV, whereupon a loud click will be heard in the receiver TR. A lesser contact resistance in the pull-bar assembly X1 will produce a softer click in the receiver TR. Thus, the intensity of the click will depend on the con` tact resistance of the swinger of the pull-bar assembly X1 upon reaching. its upper contact. A similar result will be observed if the pull-bar assembly X1 is improperly tensioned, or if there isa lack of Contact follow.

It was assumed hereinabove that in response to a character, such as X, the swinger of the pull-bar assembly X1 closed its upper contact before the swinger of the universal assemblyUV closed its upper contact and that the swinger of the universal assembly UV released its upperY contact before the swinger of the` pull-baras-Y sembly X1 released its upper contact. This produced a complete masking of the universalrcontact closure time and failed to operate the receiver TR. However, although seemingly inY good mechanical adjustment, the pull-bar assemb1yX1 may produce clicks in receiver TR. Such clicks in receiver TR may be caused when, in response to a teletype'writer character X received from the transmitter-distributor TTY, .the swinger of the universal assembly UV closes its'upper contact before the swinger of the pullbar assemblyV X1 closes its upper contact.. Under such conditions current will ow from battery B through the swinger of the universal vcontact UV previously traced and this current will ow until the swinger of the pull-bar assembly X1 closes its upper contact. This ilow of current will of course actuate the receiver TR. Such clicks in the receiver TR may also be caused when the swinger of the pull-bar assembly X1 re;

leases before the swinger of the universal assemblyUV releases in response to a teletypewriter' character X received from the transmitter-dis# tributor TTY. In the latter case the circuit through the swinger of the pull-bar assembly X1 will be established before the parallel circuit through the swinger of the universal assembly UV is established, but the current from battery B will be diverted to the latter parallel circuit of the universal contact as soon as the swinger of the pull-bar assembly X1 opens its circuit. Thus, clicks will be heard in receiver TR at any time when the contact closure time of the pullbar assembly fails to fully overlap or mask the universal contact closure time. The overlapping time is usually between about twenty and thirty milliseconds.

The time of closure of the universal contact UV may also be obtained with the apparatus of this invention. The key K is iirst closed and the motor of the non-typing selector is turned over by hand until the upper contact of the universal assembly UV is closed. The reading on meter A is then noted. The motor of the non-typing selector is then started `and the Letters signal is then transmitted repeatedly as before by having the transmitter-distributor TTY free running. The reading on meter A is again noted.

The closure time is then calculated from the formula C XE D where C is the first-noted reading on meter A,

D is the second-noted reading on meter A and E is the time required to transmit each character. In a '75 speed machine, E is about 130 milliseconds. Here is an example merely for illustration: if C is 5.0 milli-amperes and D is 1.8 milliamper-es, then the universal contact closure time willbe about 47 milliseconds.

The time of closure of any pull-bar contact such as X1 may be obtained by holding key K closed and again observing meter A to obtain the steady current value when the motor is turned over by hand until the upper contact of the universal assembly UV is again closed. The motor of the non-typing selector is then started and the character X is repeatedly transmitted as before and the reading on meter A is again noted. The closure time of the pull-bar contact may be obtained from the formula given above. It will be understood, of c0urse,that for any given installation and apparatus, meter A may be calibrated to read the closure time directly.

The overlapping time ordinarily corresponds to the closure time of the universal contact. The difference between the closure time of a particular pull-bar assembly such as X1 and the closure time of the universal assembly UV corresponds to the interval when no overlap occurs.

The apparatus and circuit described hereinabove for testing the closure times of the various contacts of a non-typing selector as well as their overlap are simple and relatively inexpensive.

The arrangement performs satisfactorily. The

arrangement may be applied to any form of teletypewriter apparatus having similar elements.

While this invention has been shown and described in certain particular embodiments merely for illustrative purposes, it will be understood 6 that the general principles of this invention may be applied to other and widely varied organizations without departing from the spirit of the invention and the scope of the appended claims.

What is claimed is:

l. An arrangement for testing a non-typing selector to determine whether the operating times of its pull-bar contacts overlap the operating time of its universal contact comprising, in addition to the pull-bar contacts and the universal contact of said non-typing selector, a source of voltage connected between all of the pull-bar contacts and their swingers, and a detector connected between all` of the pull-bar contacts and the universal swinger, the swingers of the pullbars being connected in parallel to the universal contact, said non-typing selector being connected to a source of teletypewriter signals.

2. A testing arrangement comprising a nontyping selector having a pull-bar swinger and a universal swinger together with a magnet for controlling the operation of the pull-bai swinger against its contact as well as the operation of the universal swinger against its contact, a source of voltage connected between the pull-bar contact and the pull-bar swinger, the pull-bar swinger being connected to the universal contact, a detecting device connected between the universal swinger and the pull-bar contact, and a source of teletypewriter signals connected to the magnet of said non-typing selector.

3. The combination of teletypewriter apparatus having a plurality of pull-bar swingers and their corresponding contacts and a universal swinger and its corresponding contact, together with a magnet for selectively operating the plurality of pull-bar swingers against their contacts and the universal swinger against its contact, a teletypewriter transmitter-distributor connected to said magnet, the various pull-bar swingers being connected to each other and to the universal contact, a source of voltage one terminal of which is connected to all of the pull-bar contacts and its other terminal to all of the pull-bar swingers, and a detector connected between the universal swinger and all of the pull-bar contacts.

4. An arrangement for testing a non-typing selector to determine whether the time during which any one of its pull-bar swingers closes its contact fully overlaps the time during which the universal swinger closes its contact comprising, in addition to the pull-bar swingers and the universal swinger of the non-typing selector and the corresponding contacts of said swingers, a, source of voltage, a meter connected in a series circuit with said source of voltage, said series circuit being connected between all of the pull-bar swingers and all of the pull-bar contacts, all of the pull-bar swingers being connected to the universal contact, a detector connected between the universal swinger and all of the pull-bar contacts,

and a teletypewriter transmitter-distributor con-A nectecl to said non-typing selector to transmit teletypewriter signals thereto.

DANIEL ELMORE FOLEY. WALTER DANIEL JOHNSON. 

